1. Field of the Invention
The invention relates to a manometer for measuring positive pressure of breathing gases in breathing systems during positive pressure ventilation of patients. More particularly, the present invention relates to a low cost and low weight disposable manometer with a non-linear pressure range that provides the operator with adequate accuracy of the relevant breathing gas pressure, while minimizing the overall length of the manometer for ease of handling with the breathing system.
2. Description of Related Art
It is common practice to connect a manometer to a breathing system for monitoring the pressure near the connection of the breathing system to the patient. Often this procedure is performed by connecting a reusable stationary manometer via a small-bore flexible hose to a monitoring port on the breathing system. However, the use of such a reusable attachment to the breathing system does include a risk of transmission of infectious diseases. This procedure is also inconvenient during the transport of a patient as well as during ventilation of a patient in a location where stationary manometers are not readily available. In recent years, there have been efforts to develop disposable manometers suitable for direct connection to disposable, portable breathing systems, such as manually operated resuscitators and hyperinflation bags.
U.S. Pat. No. 5,140,982 to Bauman discloses a resuscitator. The resuscitator includes a ventilation mask for sealing and surrounding a patient's mouth and nose, a gas flow manifold having a passage for delivering ventilating gas to the mask, and a manually collapsible gas receptacle coupled to the gas flow manifold. The resuscitator includes a modular structure for detecting gas pressure in the manifold. The modular structure includes a port communicating with the gas flow manifold to communicate gas pressure in the manifold to a bore. A plunger is mounted to the bore, and a transparent wall structure permits the observation of movement of the plunger wherein the transparent wall has indicia to indicate the pressure detected by the plunger.
U.S. Pat. No. 5,537,998 to Bauman discloses an emergency manual resuscitator with means for detecting air pressure. The resuscitator includes a elastomeric bag connected to a resuscitator assembly. The resuscitator also includes a one-way flap valve. The bag, when compressed manually, causes air to flow to the resuscitator assembly. The bag, when allowed to expand, causes air to flow into the bag past the one-way flap valve. A hollow plunger is movable when the bag is compressed. An air pressure release hole in the cylinder releases excess air pressure in the cylinder to the exterior only after the plunger has been moved by air pressure.
U.S. Pat. No. 5,557,049 to Ratner discloses a disposable manometer for use with a CPR bag. The manometer includes a chamber connected to a source of CPR air pressure via a patient breathing valve and an elongated restricted passageway. The manometer includes a dial and a pointer to indicate the pressure sensed within a manometer chamber. The pointer has an actuator stem at the center of a diaphragm forming one wall of the manometer chamber. The diaphragm is responsive to pressurized air entering the manometer chamber. The diaphragm reciprocates against the force of a biasing spring moving the pointer to indicate the pressure within the manometer chamber. The disposable manometer is intended to be used with a CPR bag or a patient breathing tube.
U.S. Pat. No. 5,606,131 to Pope discloses a piston manometer with spring constant dependent upon position. The manometer is used in a patient's breathing circuit and includes a housing forming a bore and a “slider” within the bore. The slider is movable between an at-rest position, an expanded pressure range, and a contracted pressure range. A spring is connected to the slider for urging the slider toward the at-rest position, while allowing movement of the slider in the two ranges due to the pressure in the breathing circuit. The housing is connected to the breathing circuit such that the gas pressure moves the slider from the at-rest position and into at least the expanded pressure range. At relatively low pressures the slider is moved into the expanded pressure range, and at higher pressures the slider is moved into the contracted pressure range against the force of the spring. The spring is formed by a relatively short tension spring and a relatively long tension spring.
U.S. Pat. No. 6,854,334 to Ratner discloses a negative inspiratory force manometer apparatus. The apparatus is connected by tubing to a patient. The apparatus has a manometer on one side in communication with an entrance port conveying ambient air to the patient. A spring loaded cap is depressed to block air inspired by the patient and to cause such air to move a diaphragm in the manometer so that the inspired negative air pressure of the patient can be recorded. As soon as the cap is released, a spring opens the entrance port to continue normal flow of ambient air to the patient.
It is common practice in medicine to measure the pressure of a patient's breathing with a reusable stationary manometer attached to a breathing system with a flexible hose. The use of a reusable manometer presents the risk of transmitting infectious diseases. Furthermore, the use of current reusable stationary manometers is inconvenient during patient transport and in locations where stationary manometers are not available. The medical industry lacks a disposable, economical manometer that solves these problems and that is compact and easily operated.